GH-969 Clipboard Changed

Samples/Samples/View/ClipboardPage.xaml

@@ -17,6 +17,7 @@
                 <Entry Placeholder="Enter text..." Text="{Binding FieldValue}" />
                 <Button Text="Copy to clipboard" Command="{Binding CopyCommand}" />
                 <Button Text="Paste from clipboard" Command="{Binding PasteCommand}" />
+                <Label Text="{Binding LastCopied}" />
             </StackLayout>
         </ScrollView>
     </StackLayout>

Samples/Samples/ViewModel/ClipboardViewModel.cs

@@ -1,4 +1,5 @@
-using System.Windows.Input;
+using System;
+using System.Windows.Input;
 using Xamarin.Essentials;
 using Xamarin.Forms;
 
@@ -7,6 +8,7 @@ namespace Samples.ViewModel
     class ClipboardViewModel : BaseViewModel
     {
         string fieldValue;
+        string lastCopied;
 
         public ClipboardViewModel()
         {
@@ -24,6 +26,27 @@ public string FieldValue
             set => SetProperty(ref fieldValue, value);
         }
 
+        public string LastCopied
+        {
+            get => lastCopied;
+            set => SetProperty(ref lastCopied, value);
+        }
+
+        public override void OnAppearing()
+        {
+            Clipboard.ClipboardContentChanged += OnClipboardContentChanged;
+        }
+
+        public override void OnDisappearing()
+        {
+            Clipboard.ClipboardContentChanged -= OnClipboardContentChanged;
+        }
+
+        void OnClipboardContentChanged(object sender, EventArgs args)
+        {
+            LastCopied = $"Last copied text at {DateTime.UtcNow:T}";
+        }
+
         async void OnCopy() => await Clipboard.SetTextAsync(FieldValue);
 
         async void OnPaste()

Xamarin.Essentials/Clipboard/Clipboard.android.cs

@@ -1,10 +1,14 @@
-using System.Threading.Tasks;
+using System;
+using System.Threading.Tasks;
 using Android.Content;
 
 namespace Xamarin.Essentials
 {
     public static partial class Clipboard
     {
+        static readonly Lazy<ClipboardChangeListener> clipboardListener
+            = new Lazy<ClipboardChangeListener>(() => new ClipboardChangeListener());
+
         static Task PlatformSetTextAsync(string text)
         {
             Platform.ClipboardManager.PrimaryClip = ClipData.NewPlainText("Text", text);
@@ -16,5 +20,19 @@ static bool PlatformHasText
 
         static Task<string> PlatformGetTextAsync()
             => Task.FromResult(Platform.ClipboardManager.PrimaryClip?.GetItemAt(0)?.Text);
+
+        static void StartClipboardListeners()
+            => Platform.ClipboardManager.AddPrimaryClipChangedListener(clipboardListener.Value);
+
+        static void StopClipboardListeners()
+            => Platform.ClipboardManager.RemovePrimaryClipChangedListener(clipboardListener.Value);
+    }
+
+    public class ClipboardChangeListener : Java.Lang.Object, ClipboardManager.IOnPrimaryClipChangedListener
+    {
+        public void OnPrimaryClipChanged()
+        {
+            Clipboard.ClipboardChangedInternal();
+        }
     }
 }

Xamarin.Essentials/Clipboard/Clipboard.ios.cs

@@ -1,4 +1,6 @@
-using System.Threading.Tasks;
+using System;
+using System.Threading.Tasks;
+using Foundation;
 using UIKit;
 
 namespace Xamarin.Essentials
@@ -11,10 +13,25 @@ static Task PlatformSetTextAsync(string text)
             return Task.CompletedTask;
         }
 
+        static NSObject observer;
+
         static bool PlatformHasText
             => UIPasteboard.General.HasStrings;
 
         static Task<string> PlatformGetTextAsync()
             => Task.FromResult(UIPasteboard.General.String);
+
+        static void StartClipboardListeners()
+        {
+            observer = NSNotificationCenter.DefaultCenter.AddObserver(
+                UIPasteboard.ChangedNotification,
+                ClipboardChangedObserver);
+        }
+
+        static void StopClipboardListeners()
+            => NSNotificationCenter.DefaultCenter.RemoveObserver(observer);
+
+        static void ClipboardChangedObserver(NSNotification notification)
+            => ClipboardChangedInternal();
     }
 }

Xamarin.Essentials/Clipboard/Clipboard.netstandard.tvos.watchos.tizen.cs

@@ -12,5 +12,11 @@ static bool PlatformHasText
 
         static Task<string> PlatformGetTextAsync()
             => throw ExceptionUtils.NotSupportedOrImplementedException;
+
+        static void StartClipboardListeners()
+            => throw ExceptionUtils.NotSupportedOrImplementedException;
+
+        static void StopClipboardListeners()
+            => throw ExceptionUtils.NotSupportedOrImplementedException;
     }
 }

Xamarin.Essentials/Clipboard/Clipboard.shared.cs

@@ -1,4 +1,5 @@
-using System.Threading.Tasks;
+using System;
+using System.Threading.Tasks;
 
 namespace Xamarin.Essentials
 {
@@ -12,5 +13,34 @@ public static bool HasText
 
         public static Task<string> GetTextAsync()
             => PlatformGetTextAsync();
+
+        public static event EventHandler<EventArgs> ClipboardContentChanged
+        {
+            add
+            {
+                var wasRunning = ClipboardContentChangedInternal != null;
+
+                ClipboardContentChangedInternal += value;
+
+                if (!wasRunning && ClipboardContentChangedInternal != null)
+                {
+                    StartClipboardListeners();
+                }
+            }
+
+            remove
+            {
+                var wasRunning = ClipboardContentChangedInternal != null;
+
+                ClipboardContentChangedInternal -= value;
+
+                if (wasRunning && ClipboardContentChangedInternal == null)
+                    StopClipboardListeners();
+            }
+        }
+
+        static event EventHandler<EventArgs> ClipboardContentChangedInternal;
+
+        internal static void ClipboardChangedInternal() => ClipboardContentChangedInternal?.Invoke(null, EventArgs.Empty);
     }
 }

Xamarin.Essentials/Clipboard/Clipboard.uwp.cs

@@ -26,5 +26,13 @@ static Task<string> PlatformGetTextAsync()
                 ? clipboardContent.GetTextAsync().AsTask()
                 : Task.FromResult<string>(null);
         }
+
+        static void StartClipboardListeners()
+            => WindowsClipboard.ContentChanged += ClipboardChangedEventListener;
+
+        static void StopClipboardListeners()
+            => WindowsClipboard.ContentChanged -= ClipboardChangedEventListener;
+
+        static void ClipboardChangedEventListener(object sender, object val) => ClipboardChangedInternal();
     }
 }

docs/en/FrameworksIndex/xamarin-essentials-android.xml

@@ -127,6 +127,7 @@
       <Member Id="F:Xamarin.Essentials.BrowserTitleMode.Show" />
     </Type>
     <Type Name="Xamarin.Essentials.Clipboard" Id="T:Xamarin.Essentials.Clipboard">
+      <Member Id="E:Xamarin.Essentials.Clipboard.ClipboardContentChanged" />
       <Member Id="M:Xamarin.Essentials.Clipboard.GetTextAsync" />
       <Member Id="M:Xamarin.Essentials.Clipboard.SetTextAsync(System.String)" />
       <Member Id="P:Xamarin.Essentials.Clipboard.HasText" />

docs/en/FrameworksIndex/xamarin-essentials-ios.xml

@@ -114,6 +114,7 @@
       <Member Id="F:Xamarin.Essentials.BrowserTitleMode.Show" />
     </Type>
     <Type Name="Xamarin.Essentials.Clipboard" Id="T:Xamarin.Essentials.Clipboard">
+      <Member Id="E:Xamarin.Essentials.Clipboard.ClipboardContentChanged" />
       <Member Id="M:Xamarin.Essentials.Clipboard.GetTextAsync" />
       <Member Id="M:Xamarin.Essentials.Clipboard.SetTextAsync(System.String)" />
       <Member Id="P:Xamarin.Essentials.Clipboard.HasText" />

docs/en/FrameworksIndex/xamarin-essentials-uwp.xml

@@ -114,6 +114,7 @@
       <Member Id="F:Xamarin.Essentials.BrowserTitleMode.Show" />
     </Type>
     <Type Name="Xamarin.Essentials.Clipboard" Id="T:Xamarin.Essentials.Clipboard">
+      <Member Id="E:Xamarin.Essentials.Clipboard.ClipboardContentChanged" />
       <Member Id="M:Xamarin.Essentials.Clipboard.GetTextAsync" />
       <Member Id="M:Xamarin.Essentials.Clipboard.SetTextAsync(System.String)" />
       <Member Id="P:Xamarin.Essentials.Clipboard.HasText" />

docs/en/FrameworksIndex/xamarin-essentials.xml

@@ -114,6 +114,7 @@
       <Member Id="F:Xamarin.Essentials.BrowserTitleMode.Show" />
     </Type>
     <Type Name="Xamarin.Essentials.Clipboard" Id="T:Xamarin.Essentials.Clipboard">
+      <Member Id="E:Xamarin.Essentials.Clipboard.ClipboardContentChanged" />
       <Member Id="M:Xamarin.Essentials.Clipboard.GetTextAsync" />
       <Member Id="M:Xamarin.Essentials.Clipboard.SetTextAsync(System.String)" />
       <Member Id="P:Xamarin.Essentials.Clipboard.HasText" />

docs/en/Xamarin.Essentials/Clipboard.xml

@@ -15,6 +15,25 @@
     <remarks></remarks>
   </Docs>
   <Members>
+    <Member MemberName="ClipboardContentChanged">
+      <MemberSignature Language="C#" Value="public static event EventHandler&lt;EventArgs&gt; ClipboardContentChanged;" />
+      <MemberSignature Language="ILAsm" Value=".event class System.EventHandler`1&lt;class System.EventArgs&gt; ClipboardContentChanged" />
+      <MemberSignature Language="DocId" Value="E:Xamarin.Essentials.Clipboard.ClipboardContentChanged" />
+      <MemberType>Event</MemberType>
+      <AssemblyInfo>
+        <AssemblyName>Xamarin.Essentials</AssemblyName>
+        <AssemblyVersion>1.0.0.0</AssemblyVersion>
+      </AssemblyInfo>
+      <ReturnValue>
+        <ReturnType>System.EventHandler&lt;System.EventArgs&gt;</ReturnType>
+      </ReturnValue>
+      <Docs>
+        <summary>Fires when the clipboard content changes.</summary>
+        <remarks>
+		  <para />
+		</remarks>
+      </Docs>
+    </Member>
     <Member MemberName="GetTextAsync">
       <MemberSignature Language="C#" Value="public static System.Threading.Tasks.Task&lt;string&gt; GetTextAsync ();" />
       <MemberSignature Language="ILAsm" Value=".method public static hidebysig class System.Threading.Tasks.Task`1&lt;string&gt; GetTextAsync() cil managed" />